Each cylinder of an internal combustion engine is equipped with one or more gas exchange valves (e.g., intake and exhaust valves) that are cyclically opened during normal operation to allow fuel and air into the engine and to discharge exhaust from the engine. In a conventional engine, the valves are opened by way of a camshaft/rocker arm arrangement. The camshaft includes one or more lobes oriented at particular angles corresponding to desired lift timings and amounts of the associated valves. The cam lobes are connected to stem ends of the associated valves by way of the rocker arm, one or more cam followers, and associated pushrod linkage. As the camshaft rotates, the cam lobes cause the cam follower(s) to rise and fall, thereby generating a reciprocating motion in the associated pushrod linkage. The rising motion is translated to a first pivoting end of the rocker arm, thereby forcing a second pivoting end of the rocker arm downward against the stem ends of the gas exchange valves. This pivoting motion causes the valves to lift or open against a spring bias. As the cam lobes rotate away from the rocker arm, the valves are released and allowed to return to their closed positions.
The gas exchange valves, rocker arms, cam followers, pushrods, and/or springs of conventional valve actuation systems are contained inside a housing known as a rocker base. The rocker base sits atop a cylinder head of the associated engine, and includes mounting surfaces for the components of the valve actuation system. In this position, the rocker base supports loads transmitted by the valve actuation system into the cylinder head. For example, the rocker base may include a spring pad that supports loads associated with an injection rocker arm. The rocker base may also include open spaces (e.g., in and around the spring pad) that accommodate other components (e.g., push rods, cam followers, lash adjusters, etc.) that extend through the rocker base into the cylinder head. An exemplary rocker base is disclosed in U.S. Pat. No. 8,820,284 of Mori et al. that issued on Sep. 2, 2014.
Although acceptable for some applications, conventional rocker bases may not have sufficient strength or rigidity for other applications. For example, in applications that incorporate lash-adjusters, a required clearance around the lash adjusters may necessitate a reduced size of the associated spring pad. When the spring pad is reduced in size, a strength and/or rigidity of the spring pad may also be reduced. When this happens, it may be possible for the spring pad to fail prematurely when exposed to high-spring loads.
The rocker base of the present disclosure is directed towards overcoming one or more of the problems set forth above and/or other problems of the prior art.